1. Field
This invention pertains to endoscopes in general and to arthroscopes in particular. Specifically, it provides such an instrument in a configuration which avoids the discomfort, fatigue and confusion involved with the use of conventional endoscopes, such as operating arthroscopes.
2. State of the Art
Endoscopy is the art of examining the interior of a body cavity or hollow organ by the use of a slender tubular telescopic instrument called an "endoscope." Endoscopes have been in common use since the early twentieth century. These instruments include a lens system, which may be conventional glass lenses within a rigid tube, air spaces between glass rods shaped to configurate the entrapped air pockets as lenses, optical glass fibers combined with conventional lenses, or other means; and a lighting system, which may be a direct illumination system (e.g., a tungsten light bulb) but is more often fiber light (light transferred from an external source through optical glass fibers). Endoscopes also commonly contain an irrigation system for introducing fluids, typically normal saline solution, to the region being examined. These systems are all contained within a cylindrical tubular housing, usually called a "sheath", which may be flexible, but is more often rigid. The cross-sectional configuration of the sheath normal its longitudinal axis (that is, as viewed from the distal end of the endoscope) is traditionally circular.
Examples of modern endoscopes are disclosed by United Kingdom Pat. No. 719,538 and by U.S. Pat. Nos. 3,525,332; 3,599,630; 3,608,547; 3,730,632; 3,744,906; 3,799,150; 3,818,902; 3,819,267; 3,889,662; and 4,024,858. Other U.S. patents of interest include U.S. Pat. Nos. 1,703,216; 1,747,407 and 2,120,996.
Endoscopes have been used for arthroscopic examinations for several decades. The development of arthroscopy and instruments adapted for arthroscopic examinations (arthroscopes) is described in the monograph "Arthroscopy of the Knee", Robert W. Jackson and David J. Dandy, Modern Orthopedic Monographs, 1976 Grune & Stratton, Inc., New York. From the monograph, it is apparent that the principal objective sought in developing arthroscopes has been to reduce their diameter compared to earlier endoscopes. All of the components conventional to an endoscope, namely an optical system, a lighting system, an irrigation system, and often an instrument channel, are contained within a usually rigid cylindrical sheath of approximately circular cross-section. The Watanabe 22 shown in FIG. 2-5 of the monograph utilizes a sheath slightly oval in cross-section to accommodate two crescentic bundles of light fibers for illumination. The grouping of the light fibers in this fashion is to avoid the penumbra typically present in the center of the visual field.
Examination of the knee joint, or other joints, imposes certain restrictions on procedures not normally encountered with other endoscopic examinations. For example, a persistent problem is arthroscopy has been maintaining adequate sterility. A circular cross-section is appropriate for introduction into the orifices of the genitourinary and gastrointestinal tracts or for puncturing the abdominal wall, but the introduction of conventional round arthroscopes to the knee joint tends to be traumatic because of the limited spacing between bones. Conventional arthroscopes of small cross-section are susceptible of breakage if the knee is flexed or if too much force is applied in efforts to distract the joint using the arthroscope as a lever or fulcrum. In the past, less delicate arthroscopes have necessarily been constructed within sheaths of greater diameter.
Characteristically, the use of conventional operating arthroscopes, as well as other endoscopes, requires the manipulation of instruments from the vicinity of the surgeon's ear. This practice is both awkward and fatiguing, but it is imposed by the customary location of the entry to the instrument channel at approximately the same level as the occular lens. It has long been recognized that there exists an optimum visual area for cognitive efforts and work. For example, C. T. Morgan has dilineated boundaries for the normal line of sight in the publication The Human Engineering Guide to Equipment Design. The Human Body in Equipment Design, McCormick, McGraw Hill (1976) recognizes that blind positioning movements in different directions from the body are made most accurately when they are to be straight ahead and are to be made below shoulder level. Nevertheless, currently available operating arthroscopes are structurally arranged in a fashion which forces the surgeon to maneuver instruments outside the norms established as optimum by such studies. The problems of discomfort, inefficiency, fatigue, and decreased accuracy inherent in conventional endoscopes, are compounded by the use of surgical instruments a foot or more in length. Instruments of such length are required because of the long instrument channels of conventional endoscopes.
Even those endoscopes (such as the O'Conner operating arthroscope marketed by Richard Wolf Medical Instruments Corp. of Rosemont, Ill.) with offset viewing lenses retain the disadvantages referred to herein. The instrument channels of such scopes are arranged for entry at a horizontal plane close to that of the surgeon's eye. Moreover, considerable leverage is provided by a lateral extension of the barrel which carries the lens system. This leverage tends to multiply forces applied to the viewing end of the arthroscope as those forces are translated to movement of the distal end of the scope itself or surgical apparatus associated with the scope. Unless precautions are both observed and effective, such high-force motion can be injurious to the patient, the surgical apparatus, or both.